This invention relates to helicopters, and more particularly to an ultralight helicopter with a simplified, economical and improved pitch and roll control mechanism.
The current state-of-the-art in helicopters is such that even small helicopters (e.g., the two-passenger ROBINSON.TM. R22 and the MINI.TM. 500) have control systems that are nearly as complex as the control systems of more traditional large helicopters. The control systems require a tail rotor with collective pitch control, a main rotor with collective pitch control and cyclic pitch control, a throttle control and various trim controls. The complexity of the machinery required to accomplish this generally results in a prohibitively high cost for small helicopters.
The ROBINSON.TM. R22 for example, costs on the order of $100,000-$120,000 in 1993 U.S. dollars, the same range of cost as a median house. In addition, the empty weights of these types of machines are in the vicinity of 500-1000 lb., figures far too high to meet the requirements for an ultralight aircraft under Federal Aviation Regulations (FAR) Part 103. Finally, the control complexity is such that lengthy and expensive pilot training is required in order for a pilot to develop proficiency in flying this type of conventional aircraft.
As used herein with reference to an aircraft the term "pitch" refers to the attitude of the nose of an aircraft as it rises or falls about a lateral axis relative to the tail of the aircraft. As used herein the term "yaw" refers to the angular orientation of the aircraft about a vertical axis. As used herein the term "roll" refers to the attitude of the aircraft about its longitudinal axis.
One prior solution to solving the complexity of helicopter pitch and roll control systems is disclosed in U.S. Pat. No. 3,722,830 issued to Barber on a helicopter type vehicle. This patent discloses a helicopter in which the pilot has to shift, in the fore-and-aft plane only, himself, his seat, and the control panel with a hand crank along rails inside a cabin. In addition, the motors which drive counter-rotating propellers of the vehicle described in this patent are pivotally mounted about the axis of rotation of the propellers. The position of the motors is angularly shifted during flight to shift the center of gravity of the vehicle for vehicle control. In this system, the weight shift is an auxiliary measure to the principal control mechanism using the pivotal movement of the motors, and is only used for the pitch direction. However, the pitch and roll control system in this patent is still too complex and expensive to be adapted for economical use in an ultralight helicopter.
Another prior pitch and roll control system for helicopters is disclosed in U.S. Pat. No. 4,787,573 issued to Pauchard on an aircraft with dual rotary wings. In this vehicle the pilot, seat and fuel tank are slidably mounted for movement in one plane only, on a set of bars inside the "nacelle", or cockpit. The weight shift of the pilot is the primary pitch control, but roll control is effected with differential braking of the rotor rings. Once again, this control system is too complex and expensive for use in an affordable ultralight helicopter. Furthermore, with the system of Pauchard, the weight of the pilot, seat and fuel tank are disposed in the middle of the two rotors, which could potentially result in unacceptable instability.
Yet another prior system is disclosed in U.S. Pat. No. 3,554,467 issued to Yowell on a counter-rotating rotor transmission for helicopters. This system includes a pitchable gearbox and rotor assembly fixed atop a fuselage, wherein the fore-and-aft motion of the helicopter is accomplished via tilting the rotor assembly. All other motions are controlled by deflection of the rotor's airflow using large, external, rotatable control surfaces. The complexity of the control system required to operate the rotatable control surfaces for roll control is a disadvantage of the system disclosed in the Yowell patent.
As evidenced by these prior solutions, there still exists a need for a pitch and roll control system for use in an ultralight helicopter which is simple, effective and economical.